Numerical and experimental investigation of an impeller tip clearance variation in an aero-engine centrifugal compressor with close-coupled pipe-diffuser

The subject of this paper is the experimental and numerical investigation of the influence of impeller tip clearance on the aerodynamics of a high-pressure transonic centrifugal compressor used in an aero-engine application. The overall change in aerodynamic performance of the stage, the isolated impeller and the isolated diffuser is analyzed. Local flow phenomena, responsible for the change in performance, are examined in closer detail. Experimental data from a state-of-the-art test rig, containing detailed 2D particle-image-velocimetry measurements, are used. 3D Reynolds-averaged Navier–Stokes simulations are conducted with the CFD solver turbo-machinery research aerodynamics computational environment to get a detailed insight into the flow field. This study contributes towards a better understanding of the principal flow phenomena of a centrifugal compressor with a close-coupled pipe-diffuser and the additional losses introduced in the individual compressor components by an increased impeller tip clearance. © Deutsches Zentrum für Luft- und Raumfahrt e.V. 2014.